U.S. patent application number 11/754546 was filed with the patent office on 2008-05-22 for developing unit and image forming apparatus using the same.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Cheol-young HAN, Hae-seog Jo, Hak-kyum Kim.
Application Number | 20080118280 11/754546 |
Document ID | / |
Family ID | 39417085 |
Filed Date | 2008-05-22 |
United States Patent
Application |
20080118280 |
Kind Code |
A1 |
HAN; Cheol-young ; et
al. |
May 22, 2008 |
DEVELOPING UNIT AND IMAGE FORMING APPARATUS USING THE SAME
Abstract
A developing unit to supply toner to a photosensitive medium of
an image forming apparatus to form an image thereon, including a
housing to hold a toner of a predetermined color, a developing
roller which is coupled to the housing to be rotatable in a
direction opposite to a moving direction of the photosensitive
medium, to supply the photosensitive medium with the toner, and to
form the image by potential difference, and a regulating blade
including a coupling end part coupled to the housing and a free end
part double bent with regard to the coupling end part to contact
the developing roller at a tip part thereof.
Inventors: |
HAN; Cheol-young;
(Yongin-si, KR) ; Kim; Hak-kyum; (Seoul, KR)
; Jo; Hae-seog; (Yongin-si, KR) |
Correspondence
Address: |
STANZIONE & KIM, LLP
919 18TH STREET, N.W., SUITE 440
WASHINGTON
DC
20006
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-si
KR
|
Family ID: |
39417085 |
Appl. No.: |
11/754546 |
Filed: |
May 29, 2007 |
Current U.S.
Class: |
399/284 |
Current CPC
Class: |
G03G 2215/0866 20130101;
G03G 15/0812 20130101 |
Class at
Publication: |
399/284 |
International
Class: |
G03G 15/08 20060101
G03G015/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2006 |
KR |
2006-116084 |
Claims
1. A developing unit usable in an image forming apparatus, the
developing unit comprising: a housing to hold a toner; a developing
roller disposed in the housing to supply the toner to a
photosensitive body of the image forming apparatus; a supplying
roller disposed in the housing to supply toner to the developing
roller; and a double-bent regulating blade connected to the housing
to regulate a toner layer formed on the developing roller.
2. The developing unit of claim 1, wherein the double-bent
regulating blade comprises a first bend at a position where it
connects to the housing and a second bend at a position between a
first part to connect to the housing and a second part to contact
the developing roller.
3. The developing unit of claim 2, wherein the first bend is in a
rotation direction opposite to the second bend.
4. The developing unit of claim 1, wherein the double-bent
regulating blade comprises: a coupling part to couple with the
housing; and a free end part to contact the developing roller,
wherein the free end part is bent and forms an angle .theta..sub.2
between a first part to connect to the coupling part and a second
part to contact the developing roller.
5. The developing unit of claim 4, wherein the second part
comprises: a tip part disposed at an end of the second part to
contact the developing roller, wherein the tip part is provided in
a direction favorable to a rotational direction of the developing
roller such that the tip part trails a rotation of the developing
roller and regulates the toner layer formed on the developing
roller.
6. The developing unit of claim 4, wherein the double-bent
regulating blade is disposed such that the coupling part is at a
position higher than a center of the developing roller.
7. The developing unit of claim 6 wherein the angle .theta..sub.2
is about 40.degree..ltoreq..theta..sub.2 .ltoreq.60.degree..
8. The developing unit of claim 1, wherein an angle .phi. between a
line connecting a contact point of the double-bent regulating blade
and a center of the developing roller and a line connecting the
center of the developing roller and a center of the supplying
roller is about 30.degree..ltoreq..phi..ltoreq.90.degree..
9. The developing unit of claim 7, wherein an angle .phi. between a
line connecting a contact point of the double-bent regulating blade
and a center of the developing roller and a line connecting the
center of the developing roller and a center of the supplying
roller is about 30.degree..ltoreq..phi..ltoreq.90.degree..
10. The developing unit of claim 1, wherein a height of the housing
is about 16mm or less.
11. The developing unit of claim 1, wherein the second bend defines
an angle .theta..sub.3 of less than 180.degree..
12. The developing unit of claim 1, wherein the double-bent
regulating blade is disposed between the developing roller and the
housing, and comprises a fixed end coupled to the housing, a tip
contacting the developing roller, a first bending part extended
from the tip part, and a second bending part extended and bent
between the first bending part and the fixed end.
13. The developing unit of claim 12, wherein the first bending part
forms an angle greater than 40.degree. with a tangential line of
the developing roller at a contact position between the tip part
and the developing roller.
14. The developing unit of claim 12, wherein the second bending
part is bent from the fixed end in a first rotation direction and
the first bending part is bent from the second bending part in a
second rotation direction opposite to the first bending
direction.
15. The developing unit of claim 14, wherein the tip part comprises
a distal end bent from the first bending part in the first rotation
direction.
16. An image forming apparatus, comprising: a photosensitive medium
to form an electrostatic latent image by being charged and exposed
to a light; a developing unit to supply a toner to the
photosensitive medium; a transfer unit to transfer the image formed
on the photosensitive unit onto a printing medium; and a fixing
unit to fix the image transferred onto the printing medium, wherein
the developing unit comprises: a housing to hold a toner, a
developing roller disposed in the housing to supply the toner to a
photosensitive body of the image forming apparatus, a supplying
roller disposed in the housing to supply toner to the developing
roller, and a double-bent regulating blade connected to the housing
to regulate a toner layer formed on the developing roller.
17. The image forming apparatus of claim 16, wherein the
double-bent regulating blade comprises a first bend at a position
where it connects to the housing and a second bend at a position
between a first part to connect to the housing and a second part to
contact the developing roller.
18. The image forming apparatus of claim 17, wherein the first bend
is in a rotation direction opposite to the second bend.
19. The image forming apparatus of claim 16, wherein the
double-bent regulating blade comprises: a coupling part to couple
with the housing; and a free end part to contact the developing
roller, wherein the free end part is bent and forms an angle
.theta..sub.2 between a first part to connect to the coupling part
and a second part to contact the developing roller.
20. The image forming apparatus of claim 19, wherein the second
part comprises: a tip part disposed at an end of the second part to
contact the developing roller, wherein the tip part is provided in
a direction favorable to a rotational direction of the developing
roller such that the tip part trails a rotation of the developing
roller and regulates the toner layer formed on the developing
roller.
21. The image forming apparatus of claim 19, wherein the
double-bent regulating blade is disposed such that the coupling
part is at a position higher than a center of the developing
roller.
22. The image forming apparatus of claim 21, wherein the angle
.theta..sub.2 is about
40.degree..ltoreq..theta..sub.2.ltoreq.60.degree..
23. The image forming apparatus of claim 16, wherein an angle .phi.
between a line connecting a contact point of the double-bent
regulating blade and a center of the developing roller and a line
connecting the center of the developing roller and a center of the
supplying roller is about
30.degree..ltoreq..phi..ltoreq.90.degree..
24. The image forming apparatus of claim 22, wherein an angle .phi.
between a line connecting a contact point of the double-bent
regulating blade and a center of the developing roller and a line
connecting the center of the developing roller and a center of the
supplying roller is about
30.degree..ltoreq..phi..ltoreq.90.degree..
25. The image forming apparatus of claim 16, wherein the developing
unit comprises at least one developing unit for each predetermined
color, and a height of the housing of each developing unit is about
16 mm or less.
26. The image forming apparatus of claim 16, wherein the second
bend defines an angle .theta..sub.3 of less than 180.degree..
27. The image forming apparatus of claim 16, wherein the
double-bent regulating blade is disposed between the developing
roller and the housing, and comprises a fixed end coupled to the
housing, a tip contacting the developing roller, a first bending
part extended from the tip part, and a second bending part extended
and bent between the first bending part and the fixed end.
28. The image forming apparatus of claim 27, wherein the first
bending part forms an angle greater than 40.degree. with a
tangential line of the developing roller at a contact position
between the tip part and the developing roller.
29. The image forming apparatus of claim 27, wherein the second
bending part is bent from the fixed end in a first rotation
direction and the first bending part is bent from the second
bending part in a second rotation direction opposite to the first
bending direction.
30. The image forming apparatus of claim 29, wherein the tip part
comprises a distal end bent from the first bending part in the
first rotation direction.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C.
.sctn.119(a) from Korean Patent Application No.2006-0116084, filed
on Nov. 22, 2006 in the Korean Intellectual Property Office, the
disclosure of which is incorporated herein in its entirety by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present general inventive concept relates to a
developing unit to supply a toner to an electrophotographic image
forming apparatus and contributes to developing an image and an
image forming apparatus using the same, and more particularly to a
developing unit having a regulating blade with an enhanced
structure to regulate a supplied toner layer and image forming
apparatus using the same.
[0004] 2. Description of the Related Art
[0005] Generally, an electrophotographic image forming apparatus
forms an electrostatic latent image by scanning light onto a
photosensitive medium charged to a predetermined electric
potential, develops the electrostatic latent image by toner of a
predetermined color, transfers the developed image to a printing
medium, and fixes the transferred image to produce a printed
image.
[0006] The electrophotographic image forming apparatus can be
divided into a wet-type and dry-type electrophotographic image
forming apparatus by its toner type, and the dry-toner type image
forming apparatus can be divided into a two-components developer
type and a one-component developer type depending on whether a
carrier is used in the developer. The two-component developer type
image forming apparatus uses a two-component developer which
includes a carrier and a toner mixed in a powder state,
respectively. The one-component developer type image forming
apparatus uses a one-component developer which includes only the
toner without the carrier.
[0007] The image forming apparatus includes a photosensitive medium
which forms an electrostatic latent image by being charged and
exposed to light, and a developing unit which supplies the
photosensitive medium with the toner to form the image.
[0008] FIG. 1 is a partial sectional view illustrating a
conventional developing unit employed in the one-component
developer type image forming apparatus. As illustrated in FIG. 1,
the conventional developing unit includes a housing 3 filled with
toner T of a predetermined color, a developing roller 5 and a
supplying roller 7 both supplying a photosensitive medium 1 with
the toner T. and a regulating blade 9 regulating a toner layer
formed on the developing roller 5.
[0009] The supplying roller 7 contacts with the developing roller 5
and rotates in the same direction in which the developing roller 5
rotates. Therefore, the toner in the housing 3 is friction-charged
at a nip which is formed between the developing roller 5 and the
supplying roller 7, and is supplied to the developing roller 5 by a
potential difference between bias-voltages applied to the
developing roller 5 and the supplying roller 7.
[0010] The developing roller 5 is coupled to the housing 3 to be
rotatable opposite to the photosensitive medium 1. The developing
roller 5 supplies the photosensitive medium 1 with the toner and
develops an image on an area of the electrostatic latent image,
which is formed at a surface of the photosensitive medium 1, by its
potential difference with the photosensitive medium 1.
[0011] The regulating blade 9 contacts with the developing roller 5
and regulates the toner layer, which is formed by the toner
supplied to a surface of the developing roller 5, to have a
predetermined thickness. To this end, the regulating blade 9
includes a free end part 9a which is bent accordingly by an
external pressure, and a fixed end part 9c which fixes the free end
part 9a to the housing 3.
[0012] In this case, for the toner layer to uniformly have a
thickness which is about 1.5 times larger than the average diameter
of a toner particle, a tip pressure which acts on a tip part 9b
where the free end part 9a contacts with the developing roller 5 is
required to be maintained beyond a predetermined value. On the
other hand, the tip pressure is influenced by a change of a
regulating angle .degree..sub.1 which is defined by a surface of
the free end part 9a and a tangent line formed by a contact between
the free end part 9a and the developing roller 5 at the tip part
9b. That is, under the same conditions, the larger the regulating
angle .degree..sub.1 becomes, the smaller the tip pressure is
required to regulate the thickness of the toner layer formed on the
developing roller 5.
[0013] If the regulating angle .degree..sub.1 becomes increased to
lower the tip pressure, the height H of the housing 3 becomes
larger. Therefore, an overall height of the developing unit may be
larger if the developing unit of a structure as illustrated in FIG.
1 is provided plurally to correspond to each color and if each of
the developing units is provided at a side of the photosensitive
medium 1 of a drum type thus forming a color image forming
apparatus of a multi-path type. Therefore, according to the above
conventional developing unit, the overall height of the image
forming apparatus becomes larger. Also, a diameter of the
photosensitive drum should be larger if the drum type
photosensitive medium 1 is employed, or otherwise a belt type
photosensitive medium 1 should be employed.
[0014] On the other hand, if the regulating blade 9 is provided so
that the regulating angle .degree..sub.1 may be about 24.degree. to
miniaturize the overall size of the developing unit, the toner
layer may have a uniform thickness when the tip pressure acting on
the tip part 9b where the free end part 9a contacts with the
developing roller 5 is maintained beyond a predetermined value, for
example, 50 gf/cm.
[0015] However, if the tip pressure of the regulating blade is
maintained beyond 50 gf/cm as described above, an excessive stress
is applied to the toner. Therefore, a deterioration of the toner,
such as a separation or a depression of an external additive
included in the toner, may occur and the image developed on the
photosensitive medium may be deteriorated. Also, the developing
roller 5 may be worn by a high tip pressure thus shortening its
life time.
[0016] Also, the toner layer formed on the developing roller 5 may
be non-uniform if the tip pressure of the regulating blade is
decreased while maintaining the regulating angle .degree..sub.1 to
be about 24.degree.. Accordingly, the toner supplied to the
photosensitive medium 1 may be insufficiently charged at a
predetermined area, so that the toner may be developed at an
unwanted position on the photosensitive medium.
SUMMARY OF THE INVENTION
[0017] The present general inventive concept provides a developing
unit having a structure to form a toner layer using a relatively
low tip pressure and image forming apparatus using the same.
[0018] Additional aspects and utilities of the present general
inventive concept will be set forth in part in the description
which follows and, in part, will be obvious from the description,
or may be learned by practice of the present general inventive
concept.
[0019] The foregoing and/or other aspects and utilities of the
present general inventive concept can be achieved by providing a
developing unit usable in an image forming apparatus, the
developing unit comprising a housing to hold a toner, a developing
roller disposed in the housing to supply the toner to a
photosensitive body of the image forming apparatus, a supplying
roller disposed in the housing to supply toner to the developing
roller, and a double-bent regulating blade connected to the housing
to regulate a toner layer formed on the developing roller.
[0020] The double-bent regulating blade may comprise a first bend
at a position where it connects to the housing and a second bend at
a position between a first part to connect to the housing and a
second part to contact the developing roller.
[0021] The first bend may be in a rotation direction opposite to
the second bend.
[0022] The double-bent regulating blade may comprise a coupling
part to couple with the housing, and a free end part to contact the
developing roller, wherein the free end part is bent and forms an
angle .theta..sub.2 between a first part to connect to the coupling
part and a second part to contact the developing roller.
[0023] The second part may comprise a tip part disposed at an end
of the second part to contact the developing roller, wherein the
tip part is provided in a direction favorable to a rotational
direction of the developing roller such that the tip part trails a
rotation of the developing roller and regulates the toner layer
formed on the developing roller.
[0024] The double-bent regulating blade can be disposed such that
the coupling part is at a position higher than a center of the
developing roller.
[0025] The angle .theta..sub.2 may be about
40.degree..ltoreq..theta..sub.2.ltoreq.60.degree..
[0026] An angle .phi..sub.2 between a line connecting a contact
point of the double-bent regulating blade and a center of the
developing roller and a line connecting the center of the
developing roller and a center of the supplying roller may be about
30.degree..ltoreq..phi..ltoreq.90.degree..
[0027] A height of the housing may be about 16 mm or less.
[0028] The second bend may define an angle .theta..sub.3 of less
than 180.degree..
[0029] The double-bent regulating blade may be disposed between the
developing roller and the housing, and may comprise a fixed end
coupled to the housing, a tip contacting the developing roller, a
first bending part extended from the tip part, and a second bending
part extended and bent between the first bending part and the fixed
end.
[0030] The first bending part may form an angle greater than
40.degree. with a tangential line of the developing roller at a
contact position between the tip part and the developing
roller.
[0031] The second bending part may be bent from the fixed end in a
first rotation direction and the first bending part may be bent
from the second bending part in a second rotation direction
opposite to the first bending direction.
[0032] The tip part may comprise a distal end bent from the first
bending part in the first rotation direction.
[0033] The foregoing and/or other aspects and utilities of the
present general inventive concept can also be achieved by providing
an image forming apparatus, comprising a photosensitive medium to
form an electrostatic latent image by being charged and exposed to
a light, a developing unit to supply a toner to the photosensitive
medium, a transfer unit to transfer the image formed on the
photosensitive unit onto a printing medium, and a fixing unit to
fix the image transferred onto the printing medium, wherein the
developing unit comprises a housing to hold a toner, a developing
roller disposed in the housing to supply the toner to a
photosensitive body of the image forming apparatus, a supplying
roller disposed in the housing to supply toner to the developing
roller, and a double-bent regulating blade connected to the housing
to regulate a toner layer formed on the developing roller.
[0034] The double-bent regulating blade may comprise a first bend
at a position where it connects to the housing and a second bend at
a position between a first part to connect to the housing and a
second part to contact the developing roller.
[0035] The first bend may be in a rotation direction opposite to
the second bend.
[0036] The double-bent regulating blade may comprise a coupling
part to couple with the housing, and a free end part to contact the
developing roller, wherein the free end part is bent and forms an
angle .theta..sub.2 between a first part to connect to the coupling
part and a second part to contact the developing roller.
[0037] The second part may comprise a tip part disposed at an end
of the second part to contact the developing roller, wherein the
tip part is provided in a direction favorable to a rotational
direction of the developing roller such that the tip part trails a
rotation of the developing roller and regulates the toner layer
formed on the developing roller.
[0038] The double-bent regulating blade may be disposed such that
the coupling part is at a position higher than a center of the
developing roller.
[0039] The angle .theta..sub.2 may be about
40.degree..ltoreq..theta..sub.2.ltoreq.60 .degree..
[0040] An angle .phi. between a line connecting a contact point of
the double-bent regulating blade and a center of the developing
roller and a line connecting the center of the developing roller
and a center of the supplying roller may be about
30.degree..ltoreq..phi..ltoreq.90.degree..
[0041] The developing unit may comprise at least one developing
unit for each predetermined color, and a height of the housing of
each developing unit may be about 16 mm or less.
[0042] The second bend may define an angle .theta..sub.3 of less
than 180.degree..
[0043] The double-bent regulating blade may be disposed between the
developing roller and the housing, and may comprise a fixed end
coupled to the housing, a tip contacting the developing roller, a
first bending part extended from the tip part, and a second bending
part extended and bent between the first bending part and the fixed
end.
[0044] The first bending part may form an angle greater than
40.degree. with a tangential line of the developing roller at a
contact position between the tip part and the developing
roller.
[0045] The second bending part may be bent from the fixed end in a
first rotation direction and the first bending part may be bent
from the second bending part in a second rotation direction
opposite to the first bending direction.
[0046] The tip part may comprise a distal end bent from the first
bending part in the first rotation direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] These and/or other aspects and utilities of the present
general inventive will become apparent and more readily appreciated
from the following description of the embodiments, taken in
conjunction with the accompanying drawings of which:
[0048] FIG. 1 is a partial sectional view illustrating a
conventional developing unit employed in a one-component type image
forming apparatus;
[0049] FIG. 2 is a schematic sectional view illustrating a
developing unit according to an exemplary embodiment of the present
general inventive concept;
[0050] FIG. 3 is a sectional view illustrating dispositions of a
regulating blade according to changes of an angle .phi. and a
regulating angle .theta..sub.2;
[0051] FIG. 4 is a three-dimensional graph illustrating a change of
an M/A value according to changes of an angle .phi. and a
regulating angle .theta..sub.2; and
[0052] FIG. 5 is a sectional view schematically illustrating an
electrophotographic image forming apparatus according to an
exemplary embodiment of the present general inventive concept.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0053] Reference will now be made in detail to the embodiments of
the present general inventive concept, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to like elements throughout. The embodiments are
described below so as to explain the present general inventive
concept by referring to the figures.
[0054] FIG. 2 is a schematic sectional view illustrating a
developing unit according to an exemplary embodiment of the present
general inventive concept.
[0055] As illustrated in FIG. 2, a developing unit according to an
exemplary embodiment of the present general inventive concept may
include a housing 21 filled with a toner T of a predetermined
color, a developing roller 23 coupled to the housing 21, and a
regulating blade 30.
[0056] The developing roller 23 can be coupled to the housing 21 to
be rotatable such that a surface of the developing roller 23 is
partially exposed to an outside of the housing 21. The developing
roller 23 supplies a photosensitive medium 10 with the toner T and
develops an image thereon by a potential difference.
[0057] The regulating blade 30 regulates a supply amount of the
toner which is supplied from the developing roller 23 to the
photosensitive medium 10. Also, the regulating blade 30 prevents
the toner T filled in the housing 21 from draining to the outside
of the housing 21 through a part where the developing roller 23 is
coupled.
[0058] To this end, the regulating blade 30 may include a coupling
end part 31 coupled to the housing 21, and a free end part 35 bent
twice with regard to the coupling end part 31 and having a tip part
36a to contact the developing roller 23. The free end part 35 is
bent freely by an external pressure, and includes a first bending
part 36 having the tip part 36a to contact the developing roller 23
and a second bending part 38 formed between the first bending part
36 and the coupling end part 31. Therefore, a regulating angle
.theta..sub.2 formed between the first bending part 36 and the
developing roller 23 may be increased while a height of the housing
21 is decreased by double bending the first and the second bending
parts 36 and 38. Accordingly, a toner layer L may be formed
uniformly on the developing roller 23 while a tip pressure of the
tip end part 36a is lowered.
[0059] Hereinafter, a disposition of the regulating blade 30 is
described in detail. The coupling end part 31 can be positioned at
a side higher than a center of the developing roller 23. Also, as
illustrated in FIG. 2, the regulating blade 30 can be provided in a
direction favorable to a rotational direction of the developing
roller 23 so that the tip part 36a of the free end part 35 may be
trailed when the developing roller 23 rotates. Therefore, the
regulating blade 30 can be prevented from being turned over when
the developing roller 23 is driven to rotate.
[0060] The regulating angle .theta..sub.2 can satisfy a condition 1
such that the toner layer L is regulated to be uniformly formed
while the tip pressure of the free end part 35 is maintained below
45 gf/cm.
40.degree..ltoreq..theta..sub.2.ltoreq.60.degree. <Condition
1>
where the regulating angle .theta..sub.2 is an angle between a bent
surface C in the tip part 36a of the first bending part 36 and a
tangent line D which is formed by the tip part 36a contacting with
the developing roller 23 at a position A.
[0061] If the regulating angle .theta..sub.2 is set to satisfy the
condition 1 while a condition 2, described below, is also
satisfied, a weight of the toner per unit area (M/A) may be
maintained from about 0.45 to 0.7 mg/cm.sup.2 where the tip
pressure of the regulating blade 30 is below 40 gf/mm, and a
charging amount per unit weight of the toner (Q/M) may be
maintained at about -10 to -23 pC/g in a normal temperature and
humidity environment.
[0062] On the other hand, if the regulating angle .theta..sub.2 is
below about 40.degree., the tip pressure can be excessively lowered
and the M/A value can be increased. Therefore, a regulation of the
toner layer L through the regulating blade 30 is weakened, making
it difficult to uniformly form the toner layer L.
[0063] If the regulating angle .theta..sub.2 is beyond about
60.degree., the M/A value is increased and it is may be easy to
regulate the toner layer L through the regulating blade 30.
However, the tip pressure of the regulating blade 30 is also
increased and a problem, such as an excessive stress applied to the
toner, occurs. Also, as a supplying roller 25 to be described later
can be positioned lower than the developing roller 23, a problem
that an overall height of the housing 21 becomes large can
occur.
[0064] The first bending part 36 and the second bending part 38 may
have inside surfaces facing the developing roller 23 to form an
angle .theta..sub.3 of less than 180.degree.. The tip part 36a may
include a distal end extended from the second bending part 38 in a
direction opposite to the first bending part 36 with respect to a
contact point between the developing roller 23 and the free end
part 35. The free end part 35 is bent, that is, the second bending
part 38 is bent from the coupling part 31 in a first rotation
direction, the first bending part 36 is bent from the second
bending part 38 in a second rotation direction, and the distal end
of the tip part 36a can be bent from the first bent part 36 in a
third rotation direction similar to the first rotation
direction.
[0065] The developing unit according to the exemplary embodiment of
the present general inventive concept may further include a
supplying roller 25 provided in the housing 21. The supplying
roller 25 rotates and supplies the developing roller 23 with the
toner T. For example, the supplying roller 25 may include a sponge
or other materials to attach the toner on its outer surface such
that a width of its contact nip with the developing roller 23 may
be enlarged when the supplying roller 25 supplies toner T to the
developing roller 23 by contacting the developing roller 23 at the
contact nip.
[0066] The supplying roller 25 helps a supply flow of the toner to
be easily performed as well as attaches the toner T onto the
developing roller 23. Accordingly, to easily perform the toner
supply, a bias power source of a predetermined electric potential
is applied from a power supplying device (not illustrated) to the
supplying roller 25. The toner supplied by the application of the
bias power source is charged to have a predetermined electric
potential. Also, after developing, the supplying roller 25 can
clean the toner T remaining on the developing roller 25.
[0067] To this end, a rotational direction of the supplying roller
25 and a disposition of the supplying roller 25 need to be
considered in connection with the regulating blade 30.
[0068] That is, the supplying roller 25 can rotate in a same
direction in which the developing roller 23 rotates, which is a
counterclockwise direction in the exemplary embodiment illustrated
in FIG. 2. Therefore, surfaces of the developing roller 23 and the
supplying roller 25 can move in opposite directions at the contact
part therebetween to effectively clean the toner remaining on the
developing roller 23 after the developing roller 25 supplies the
toner to the photosensitive medium 10 as well as to effectively
friction charge the toner supplied from the supplying roller 25 to
the developing roller 23.
[0069] Hereinafter, a disposition of the supplying roller 25 is
described. If an angle .phi. is an angle between a line OA and a
line OB, where the line OA is a line connecting a position A where
the regulating blade 30 contacts with the developing roller 23 with
a center O of the developing roller 23, and where the line OB is a
line connecting the center O of the developing roller 23 with a
center B of the supplying roller 25, the angle .phi. can satisfy a
condition 2 described below.
30.degree..ltoreq..phi..ltoreq.90.degree. <Condition 2>
[0070] If the angle .phi. satisfies condition 2, the tip pressure
may be maintained comparably lower than about 45 gf/cm if condition
1 is also satisfied. Also, the M/A value and the Q/M value by which
the thickness of the toner layer L is determined may satisfy a
condition of the predetermined range described above, and the
height of the housing 21 may be lowered to within about 16 mm.
[0071] The ranges of the condition 1 and 2 have been derived from a
result of a test as follows.
[0072] FIG. 3 is a sectional view illustrating dispositions of a
regulating blade 30 according to changes of a regulating angle
.theta..sub.2 and an angle .phi..
[0073] FIG. 4 is a three-dimensional graph illustrating a change of
an M/A value according to changes of the regulating angle
.theta..sub.2 and the angle .phi. which are measured according to a
change of the disposition of the regulating blade 30 of FIG. 3.
[0074] Table 1 indicates tip pressures F, the M/A and the Q/M
values which are measured when the regulating angle .theta..sub.2
is changed by 10.degree. in a range of 20.degree. to 80.degree.
when the angle .phi. is also changed by 10.degree. to 20.degree. in
a range of 20.degree. to 100.degree..
[0075] The regulating blade 30 used in the above test is a
stainless steel plate which has a sectional shape double bent as
illustrated in FIG. 3 and has a thickness of 0.07 mm. Then, the
regulating blade 30 is spot-welded on a cold rolled bracket 22 in
place of the housing. The angle .phi. and the regulating angle
.theta..sup.2 are set in the above ranges.
[0076] The toner (not illustrated) used in the test is a polyester
based powder toner having a diameter of 8 .nu.m, the developing
toner 23 is made of Nitrilo Butadiane rubber, and the supplying
roller 25 is made of Nylon pelt brush.
TABLE-US-00001 TABLE 1 Sample .phi. .theta..sub.2 F M/A Q/M No.
[.degree.] [.degree.] [gf/cm] [mg/cm.sup.2] [.mu.C/g] #1 20 20 24
0.83 -5 #2 20 30 26 0.80 -5 #3 20 40 28 0.78 -5 #4 20 50 29 0.75 -5
#5 20 60 29 0.74 -6 #6 20 70 30 0.73 -7 #7 20 80 30 0.71 -8 #8 30
20 29 0.74 -6 #9 30 30 30 0.73 -7 #10 30 40 33 0.64 -15 #11 30 50
35 0.61 -17 #12 30 60 39 0.49 -21 #13 30 70 32 0.44 -25 #14 30 80
43 0.41 -28 #15 40 20 30 0.73 -7 #16 40 30 31 0.72 -8 #17 40 40 34
0.63 -16 #18 40 50 36 0.60 -18 #19 40 60 38 0.48 -22 #20 40 70 41
0.43 -26 #21 40 80 44 0.40 -29 #22 60 20 31 0.72 -8 #23 60 30 31.5
0.71 -9 #24 60 40 33 0.62 -17 #25 60 50 34 0.59 -19 #26 60 60 38
0.47 -23 #27 60 70 42 0.42 -27 #28 60 80 45 0.39 -30 #29 80 20 32
0.76 -7 #30 80 30 34 0.72 -9 #31 80 40 35 0.60 -19 #32 80 50 39
0.57 -21 #33 80 60 42 0.45 -25 #34 80 70 44 0.40 -29 #35 80 80 46
0.37 -32 #36 90 20 35 0.75 -6 #37 90 30 36 0.73 -8 #38 90 40 38
0.59 -20 #39 90 50 42 0.56 -22 #40 90 60 44 0.45 -25 #41 90 70 46
0.39 -30 #42 90 80 47 0.36 -33 #43 100 20 38 0.46 -24 #44 100 30 39
0.43 -27 #45 100 40 41 0.38 -31 #46 100 50 43 0.35 -34 #47 100 60
46 0.32 -35 #48 100 70 48 0.30 -36 #49 100 80 49 0.28 -38
[0077] Table 1 illustrates values for the regulating angle
.theta..sub.2 and the angle .phi. where the toner weight per unit
area (M/A), meaning the thickness of the toner layer formed on the
surface of the developing roller, is about 0.45 to 0.7 mg/cm.sup.2
and where the charging amount per unit toner weight (Q/M) satisfies
the range of -10 to -23 .mu.C/g, which are values for the
regulating angle .theta..sub.2 and the angle .phi. in the ranges of
conditions 1 and 2, respectively.
[0078] M/A values between about 0.45 to 0.7 mg/cm.sup.2 are
selected because they represent a conversion of the toner layer L
formed to have a thickness of about 1.3 to 2 times larger than a
diameter of a toner particle on the developing roller 23 when a
commercialized non-magnetic one component developer is used. If the
M/A value deviates from its upper limit value (0.7 mg/cm.sup.2),
the Q/M value is lowered. Accordingly, in this case, it is
difficult to control transfer of the toner from the developing
roller to the photosensitive medium and transferring the toner
image from the photosensitive medium to a printing medium or an
intermediate transfer medium.
[0079] Also, quality of the image is deteriorated due to a
background phenomenon where the toner moves beyond the image on the
printing medium.
[0080] If the M/A value deviates from its lower limit value (0.45
mg/cm.sup.2), the Q/M value is raised. Accordingly, in this case an
electric discharge can easily occur at a developing gap between the
developing roller and the photosensitive media if a non-contact
developing type developer is used where there is a developing value
between the photosensitive medium and the developing roller.
Therefore, since an electric field, which is less than that at the
electric discharge, should be generated, the electric field becomes
weak and a sufficient number of the toner particles may not be
transferred to the photosensitive medium, so that an appropriate
developing density cannot be obtained on the photosensitive medium.
Such a phenomenon may be even worse when the developing unit is
under a low temperature and low humidity. That is, as the Q/M value
is raised under low temperature and low humidity conditions, it is
even harder to obtain a target density of toner on the
photosensitive medium.
[0081] Also, although the electric discharge does not occur between
the developing roller and the photosensitive medium when a contact
type developer, where the developing roller contacts with the
photosensitive medium, is used, the M/A value becomes low.
Therefore, a strong electric field should be applied to obtain a
required density. In this case, even if the target density is
obtained on the photosensitive medium under the strong electric
field, the electric discharge is generated. Accordingly, the
sufficient density cannot be obtained from the image transferred
onto the printing medium.
[0082] Therefore, by disposing the regulating blade and the
supplying roller to satisfy conditions 1 and 2, as in the
developing unit according to the exemplary embodiment of the
present general inventive concept illustrated in FIG. 2, the M/A
value may be maintained in the range of about 0.45 to 0.7
mg/cm.sup.2 and the Q/M value may be maintained in the range of
about -10 to -23 .mu.C/g. Also, by using the regulating blade
having a double bending structure, the height of the housing may be
lowered while satisfying the regulating angle of condition 1.
[0083] While only one developing unit is described as an example of
the present general inventive concept in the above embodiment, the
present general inventive concept is not limited thereto, and a
plurality of the developing units can be used in a multi-path type
image forming apparatus according to the present general inventive
concept.
[0084] FIG. 5 is a sectional view schematically illustrating an
electrophotographic image forming apparatus according to an
exemplary embodiment of the present general inventive concept.
[0085] As illustrated in FIG. 5, the electrophotographic image
forming apparatus may include a cabinet 110, a photosenstive medium
120 provided in the cabinet 110, a light scanning unit 125, a
transfer unit 127, a developing unit 130, and a fixing unit
150.
[0086] The photosensitive medium 120 can be charged by a charging
roller 123 to form an electrostatic latent image thereon by being
exposed to a beam scanned by the light scanning unit 125. As
illustrated in FIG. 5, the photosensitive medium 120 may include a
metallic drum of a cylinder shape having a photoconductive layer
formed on an outer circumference of the metallic drum.
[0087] The charging roller 123 can be an electric charger to charge
the photosensitive medium 120 to a uniform electric potential. The
charging roller 123 supplies an electric charge while rotating in
contact or in non-contact with the photosensitive medium 120, thus
enabling the photoconductive layer of the photosensitive medium 120
to have a uniform electric potential. Alternatively, a corona
electric charger (not illustrated) may be used in place of the
charging roller 123.
[0088] The light scanning unit 125 can be provided at a lower side
of the photosensitive medium 120, and scans a light to the
photosensitive medium 120 charged to the uniform electric potential
to form the electrostatic latent image corresponding to image
information.
[0089] The developing unit 130 may include first to fourth
developing units 130C, 130M, 130Y, and 130K which can be divided by
color. Each of the first to the fourth developing units 130C, 130M,
130Y, and 130K may contain a toner of a solid powder state having a
color of cyan, magenta, yellow, and black, respectively. Each of
the first to the fourth developing units 130C, 130M, 130Y and 130K
may include a developing roller 135 respectively to supply the
photosensitive medium 120 with the toner and to form the toner
image for the electrostatic latent image formed on the
photosensitive medium 120. In this case, a developing gap of about
tens to hundreds microns can be formed between the developing
roller 135 and the photosensitive medium 120, thus enabling
non-contact developing of the latent image. When the developing is
performed on the photosensitive medium 120 through the first to the
fourth developing units 130C, 130M, 130Y, and 130K, only one
developing roller 135 of the developing unit corresponding to one
color may contribute to the developing for each rotation of the
photosensitive medium 120.
[0090] Each developing unit 130 may include a housing, a developing
roller, a supplying roller and a regulating blade (not
illustrated). The structure and the disposition of the regulating
blade and the disposition of the supplying roller are determined to
satisfy conditions 1 and 2. Therefore, when the first to the fourth
developing units 130C, 130M, 130Y, and 130K are used as illustrated
in FIG. 5, a height of the housing of the developing units may be
controlled to be about 16 mm while a tip pressure of the regulating
blade can be lowered by increasing a regulating angle. Therefore,
the overall structure, including the photosensitive medium 120, may
be compact. As the constitution of each developing unit 130 is
similar as that of the developing unit according to the embodiment
of the present general inventive concept which has been described
with reference to FIG. 2, a detail description is omitted.
[0091] The transfer unit 127 receives the image developed on the
photosensitive medium 120 and transfers the image to a printing
medium P. The toner image of each color sequentially formed on the
photosensitive medium 120 is transferred onto the transfer unit 127
and is superposed therebetween to form a color image.
[0092] The image forming apparatus may include first and second
cleaning units 141 and 143, an erasing lamp 147, a power supplying
device 149, and a feeding unit 160.
[0093] When the toner image is transferred to the transfer unit
127, the first cleaning unit 141 can remove a waste toner remaining
on an outer circumferential surface of the photosensitive medium
120. The second cleaning unit 143 can remove the waste toner
remaining on the transfer unit 127 after the image transferred to
the transfer unit 127 is secondly transferred to the printing
medium P.
[0094] Before charging, the erasing lamp 147 removes the electric
charge remaining on the outer circumferential surface of the
photosensitive medium 120. That is, the erasing lamp 147 can remove
the electric charge remaining on the surface of the photosensitive
medium 120 by emitting light of a predetermined intensity onto the
outer circumferential surface of the photosensitive medium 120.
[0095] The power supply device 149 provides a developing bias power
source, a developing prevention bias power source, first and second
transfer bias power sources, and a charging bias power source. The
developing bias power source serves to develop the toner from the
first to fourth developing units 130C, 130M, 130Y, and 130K onto
the photosensitive medium 120. The developing prevention bias power
source serves to prevent the toner of the developing unit other
than that contributing to the developing from being developed onto
the photosensitive medium 120.
[0096] The first transfer bias power source is used to transfer the
toner image from the photosensitive medium 120 to the transfer unit
127, and the second transfer bias power source is used to transfer
the toner image from the transfer unit 127 to the printing medium
P. The charging bias power source is a power source applied to the
charging roller 123.
[0097] The fixing unit 150 serves to fix the toner image
transferred to the printing medium P, and may include a pair of
fixing rollers 151 and 153 which rotate in contact therebetween
with a predetermined pressure. A heating source (not illustrated)
can be provided to at least one of the pair of the fixing rollers
151 and 153. Accordingly, when the printing medium P having the
transferred image passes through the fixing unit 150, the toner
image is fused on the printing medium P by heat and pressure thus
completing the image printing process.
[0098] The feeding unit 160 can provide a space to load the
printing medium P. The printing medium P supplied through the
feeding unit 160 can be conveyed through a conveying unit 170 to a
path between the transfer unit 127 and a pressing roller 129. The
printing medium P having the printed image is discharged to an
outside through a discharging roller 179.
[0099] According to the developing unit as described above,
decreasing the tip pressure below 40 gf/cm can prevent an excessive
stress from being applied to the toner and prevent the image
developed on the photosensitive medium from being deteriorated.
Also, the developing roller is prevented from being worn by a high
tip pressure, thus extending its life time.
[0100] Also, by forming the regulating blade into a double bending
structure, the regulating angle .theta..sub.2 may be increased
without increasing the height of the housing, and the disposition
angle between the regulating blade and the supplying roller may be
optimized. Therefore, the required M/A and Q/M values may be
maintained while the tip pressure is lowered, thus preventing a
non-uniform toner layer and errors in developing and transferring
of the image.
[0101] Also, the height of the developing unit may be controlled to
be within about 16 mm, thus enabling the overall structure to be
compact and a manufacturing cost to be reduced. Also, the
disposition of the developing unit can be optimized thus improving
printing quality.
[0102] Although a few exemplary embodiments of the present general
inventive concept have been illustrated and described, it will be
appreciated by those skilled in the art that changes may be made in
these embodiments without departing from the principles and spirit
of the general inventive concept, the scope of which is defined in
the appended claims and their equivalents.
* * * * *